Operation of aircraft engines in adverse weather conditions or at high altitudes can often lead to ice forming on the exposed surfaces of gas turbine engines. This accumulation of ice on the engine surfaces limits the quantity of air flow to the engine. Such reductions in air flow can result in a reduction of power output, efficiency and/or cooling capacity of the engine. Further, the ice that forms on elements of the gas turbine engine can break loose and be ingested by the engine, potentially causing damage or wear to the engine. Loose ice, airflow inconsistencies, and disturbed airflow can cause performance issues and vibration problems in downstream components of the engine and can also lead to loss of engine efficiency. To combat these issues, most gas turbine engines incorporate a de-icing system to protect the engine components from the undesirable effects of ice accumulation.
Systems and methods to prevent or remove ice formation on gas turbine engines are well known. Engine de-icing systems commonly employ a thermal source, such as hot air bleed from the engine core, which is applied to the engine inlet to melt or evaporate ice build-up on the external surfaces thereof. In earlier designs, the de-icing systems would bleed a portion of the hot gas stream flowing through the engine and direct it through passages in relation to the elements desiring heat. The bled stream then passes through ports into the air stream flowing into the engine. This heated stream causes the engine surfaces to be heated and effectively removes or prevents the accumulation of ice. However, these de-icing systems using the hot air bleed effect engine efficiency in that the extraction of air or heated fluid from the motive gas stream passing through the engine reduces the overall efficiency of the engine. The efficiency loss occurs because the air is bled from the motive gas stream at a high energy point and re-introduced at a low energy point. Mechanisms have been created to operate said de-icing systems on an “as needed” basis, either when ice is detected or suspected; however, such mechanisms add an undesired mechanical complexity to the design of the gas turbine engine.
Other methods have also been developed using electrical elements for gas turbine engine de-icing systems. In addition to, or alternatively to, using hot air bleeds, electrothermal devices have been used to prevent ice formation and to remove ice from engine components. Commonly employed electrothermal de-icers use heating elements that are operatively associated with the area for which de-icing is desired. For example, heating elements may be embedded within the surfaces of a nosecone and/or fairings of the fan of a gas turbine engine. In some recent examples of electrical de-icing systems, the system involves a series of heaters operatively associated with regions of a gas turbine engine. For example, the system may include one heater at the leading-edge of the nosecone of a gas turbine engine, a second heater located aft of the first heater, and a third heater aft of the second heater. All three heaters are electrically-powered to heat the elements of the nosecone and prevent icing of the structure. Further, these systems may employ different heating levels at the different heaters per a schedule or per temperature sensors. Such examples are further detailed in U.S. Patent Publication No. 2011/0309066 (“Engine Inlet Ice Protection System Having Embedded Variable Watt Density Heaters”).
When using electrically powered heaters, the de-icing systems generally draw power from the main electrical power source for the aircraft. This can cause an unwanted strain on the power source and also complicate the electrical wiring of the aircraft. Accordingly, it can be seen that an improved engine de-icing system is needed.